VENTILATION OF UNDERGROUND EXCAVATIONS IN OPEN PIT/UNDERGROUND COAL MINING

Ventilation of surface and underground mines in hybrid mining obeys common principles and has peculiar features of combination and interaction of open pit and underground mining technologies. Specificity of ventilation of underground excavations in hybrid mining is conditioned by the fact that these excavations are driven from the pit walls and bottom, which are the production areas of open pit mine. Air in such work areas contains much dust and vehicle exhaust gas at concentrations exceeding MAC values. Ventilation induces mixing of air flows and is complicated by the basin-like shape of open pit mine. The function of underground mine ventilation in hybrid mining method reduces to air feed from the windward side of the open pit using booster fans or stationary fan installations and outlet of return air to the mined-out area of open pit where pollution of air with gas is very high. The independent ventilation of underground excavations requires drilling of air holes on the sides or in the center of excavations as air feed pressure and velocity is such air holes are unconstrained under safety regulations. The side air inlet holes need installation of many low-head fans to ensure pre-set air flow rates in development and production headings. Such fans are not produced in lots. Thus, hybrid mining operations require a combination ventilation circuit with air holes equipped with suction pumps to discharge mine air in the atmosphere beyond the limits of open pit mine.